Lymphocytes from both normal volunteer patients and cancer patients are cryopreserved and stored for varying lengths of time. These are recovered and used in assays of cellular immune function and compared to those same assays that were done on the fresh cells. The results using normal volunteer cells have shown an ability of the cryopreserved cells to maintain a function in mitogen stimulation assays and mixed lymphocyte response assays that is similar to the fresh cells. The use of simultaneous cultures has decreased day-to-day variability over that which is seen in individual daily assays. Current methods of cryopreservation may alter the function of cells obtained from cancer patients receiving combined modality therapy. This is being evaluated. Parathyroid tissue has been frozen and stored for 1-9 months and reimplanted into the parathyroidectomized autologous animals. These endocrine tissues have been able to sustain life, normal serum calcium levels, and produce parathormone after reimplantation.